Ofatumumab and Breastfeeding

Summary of use during lactation

Information on the clinical use of ofatumumab during breastfeeding indicates that the drug has no effect on the immunity or growth of breastfed infants. The amounts in milk are extremely low. It is also likely to be partially destroyed in the infant's gastrointestinal tract and absorption by the infant is probably minimal.[1] Ofatumumab appears to be acceptable to use during breastfeeding.[2-4] Breastfeeding can resume after the injection; however, waiting for at least 2 weeks postpartum to resume therapy may minimize transfer to the infant.[5]

Drug levels in milk and infant serum

Maternal Levels. Twelve mothers (11 received a loading dose) who were receiving ofatumumab for multiple sclerosis collected milk before treatment initiation, before the next ofatumumab dose, and 24 hours after a dose at weeks 4, 8, and 12 of therapy. Additional samples were taken at either 16 days after the dose at weeks 4, 8, and 12 and 7 hours after a dose at week 12, or at 8 and 15 days after a dose at weeks 4, 8, and 12. Mothers collected between 7 and 15 milk samples. Of the 141 samples collected after ofatumumab initiation, 30.5% had a concentration below the quantification limit of 1.5 mcg/L. The median time to the peak concentration was 37 days (range 14 to 107 days) after ofatumumab treatment initiation, during which 2 to 6 ofatumumab doses were given. Milk concentration were between the quantification limit and 56.3 mcg/L, with large inter- and intra-individual variations. The average milk concentration was 4.5 mcg/L (range 2 to 12 mcg/L) and the average infant dose was 0.68 (range 0.26 to 1.77) mcg/kg daily.[3] Infant Levels. Relevant published information was not found as of the revision date.

Effects in breastfed infants

A report from the German multiple sclerosis registry found 2 infants who were breastfed (extent not stated) during ofatumumab use. No effect on the B-cell count of the infants was noted.[6,7] In a prospective cohort study, 12 women with multiple sclerosis and their breastfed infants were followed after starting ofatumumab between 0.6 and 19.6 months (median 3.9 months) postpartum. They breastfed (8 exclusively) for a median of 9.6 months (range 1.8 to 23.8 months) while taking ofatumumab. The infants were followed for a median of 23.6 months (range 12.2 to 27.0 months) postpartum. No infants had developmental delays. Ten had at least one typical childhood infection after initiation of ofatumumab, including respiratory infections, COVID-19, and hand, foot, and mouth disease. Two infants were hospitalized for respiratory syncytial virus (RSV) and bronchitis. Eight infants received live vaccines, two against RSV and eight against measles-mumps-rubella-varicella. No adverse reactions were reported after the vaccinations. None of five infants with B-cell counts taken during exposure, had counts below the lower limit of normal.[3] A follow-up study of 3 infants who were breastfed during maternal ofatumumab therapy for multiple sclerosis found no development delays over with observation period up to one year.[8] The amount of breastfeeding and other details were not provided in the abstract.

Effects on lactation and breastmilk

Relevant published information was not found as of the revision date.

Alternative drugs to consider

(Multiple Sclerosis) Glatiramer, Immune Globulin, Interferon beta, Methylprednisolone, Natalizumab, Ocrelizumab, Peginterferon beta

References

1. Anderson PO. Monoclonal antibodies during breastfeeding. Breastfeed Med 2021;16:591-333956488 PubMed
2. Dobson R, Rog D, Ovadia C, et al. Anti-CD20 therapies in pregnancy and breast feeding: A review and ABN guidelines. Pract Neurol 2022;23:6-1435803727 PubMed
3. Witt L, Dost-Kovalsky K, Friedmann N, et al. Ofatumumab-exposed breastfeeding in multiple sclerosis patients. Mult Scler 2025;31:338-5139757874 PubMed
4. Shipley J, Beharry J, Yeh W, et al. Consensus recommendations on multiple sclerosis management in Australia and New Zealand: part 2. Med J Aust 2025;222:365-7139923190 PubMed
5. Krysko KM, Dobson R, Alroughani R, et al. Family planning considerations in people with multiple sclerosis. Lancet Neurol 2023;22:350-6636931808 PubMed
6. Schwake C, Steinle J, Thiel S, et al. Effects of anti-CD20 therapies on infant health and physiological B-cell development if administered before or during pregnancy and/or lactation. Mult Scler J 2022;28 (3 Suppl):29-30.doi:10.1177/13524585221123 PubMed
7. Schwake C, Steinle J, Thiel S, et al. Neonatal B-cell levels and infant health in newborns potentially exposed to anti-CD20 monoclonal antibodies during pregnancy or lactation. Neurol Neuroimmunol Neuroinflamm 2024;11:e20026438870458 PubMed
8. Camilli F, Carrozzo G, Bandini A, et al. Maternal and neonatal outcomes of natalizumab and anti-CD20 monoclonal antibody exposure during pregnancy and lactation in multiple sclerosis. Multiple Sclerosis Journal 2025;31 (3 Suppl):1363-4.doi:10.1177/13524585251370543 PubMed